/Engine/Source/Editor/GraphEditor/Public/GraphDiffControl.h
Looks for node differences between the two supplied graphs. Diffs will be returned in the context of "what has changed from OldGraph in NewGraph?"
True if any differences were found, false if both graphs are identical.
static bool DiffGraphs ( [UEdGraph](API\Runtime\Engine\EdGraph\UEdGraph) *const OldGraph, [UEdGraph](API\Runtime\Engine\EdGraph\UEdGraph) *const NewGraph, [TArray](API\Runtime\Core\Containers\TArray)< [FDiffSingleResult](API\Runtime\Engine\FDiffSingleResult) > & DiffsOut )